In the field of refining of molten metal in a top-blowing oxygen converter, a control system based on dynamic control has been developed for the purpose of saving labor in refining operations and automating the processes. A sub-lance for obtaining information and data concerning conditions of refining in the converter such as the chemical composition and the temperature of molten metal during refining is indispensable for said control system.
Refining of a molten metal in a top-blowing converter is effected by inserting a main lance for blowing oxygen substantially vertically and downwardly into a top-blowing oxygen converter containing a molten metal to be refined, to blow pressurized oxygen onto the surface of the molten metal through the main lance at a certain position above the surface of the molten metal. On the other hand, sampling and temperature-measuring of the molten metal during refining in the converter are carried out by inserting a sub-lance into the converter substantially vertically and downwardly at a proper timing, and by immersing a probe for sampling and temperature-measuring of molten metal, which is releasably fitted to the lowermost end of the sub-lance, into the molten metal.
In general, the sub-lance is releasably fitted to a sub-lance carriage. The sub-lance carriage is suspended by a wire rope engaging with a block provided at the upper end portion of a turning frame, and moves vertically together with the sub-lance along a guide rail provided vertically on the turning frame by hoisting up or down said wire rope with the use of a winch. Sampling and temperature-measuring of the molten metal during in the converter are therefore conducted by lowering the sub-lance together with the sub-lance carriage by hoisting down the wire rope with the use of the winch, and immersing the probe fitted to the lowermost end of the sub-lance into the molten metal. The sub-lance is movable, as required, together with the sub-lance carriage, from outside to above the converter and from above the converter to outside, by turning the turning frame, for such purposes as replacement of the prove, maintenance and inspection of the sub-lance and replacement of the sub-lance.
The sub-lance usually has a concentric three-pipe structure comprising from inside to outside a gas supply pipe, a water discharge pipe and a water supply pipe, and is cooled by cooling water flowing through the water supply pipe and the water discharge pipe, during sampling and/or temperature-measuring of the molten metal. To prevent slag from coming into the probe when the probe passes through the slag layer convering the surface of the molten metal, a pressurized gas such as air and nitrogen gas is blown into the probe through the gas supply pipe.
However, the sub-lance inserted into the converter during refining of the molten metal deflects inevitably toward the main lance under the effect of the high temperature heat of the hot spot where occur reactions between oxygen blown from the main lance and the molten metal and the high temperature heat of molten metal and molten slag splashing and adhering onto the sub-lance. More specifically, the sub-lance deflects toward the main lance, under the effect of the above-mentioned heat affection, substantially in proportion to the number of repetitions of sampling and/or temperature-measuring during refining of the molten metal. Because of this deflection, it has been unavoidable that the following problems occurred in a conventional sub-lance after being used several times:
(1) It becomes difficult to immerse straight vertically the probe fitted to the lowermost end of the sub-lance into the molten metal, and this causes troubles in sampling and/or temperature-measuring; PA0 (2) The sub-lance and the probe become too close to the hot spot, or even come in the hot spot, thus causing burnout of the sub-lance and the probe; PA0 (3) The device for engaging and disengaging the probe with the lowermost end of the sub-lance becomes unserviceable; and PA0 (4) It becomes impossible for the sub-lance to pass through a through-hole provided in a hood which hangs over and covers the converter, and when the aforementioned deflection of the sub-lance is serious, it may become necessary to remove the sub-lance by flamecutting. PA0 (a) Possibility of easy and accurate detection of the angle of rotation of the sub-lance 4 ensures correction of a deflection of the sub-lance 3 toward the main lance, which occurs during refining of molten metal in a top-blowing oxygen converter. As a result, while it was necessary to replace twelve sub-lances for 1,000 repetitions of sampling and/or temperature-measuring in the conventional sub-lance assembly, it is not necessary, according to the prior art, to make any replacement of sub-lance for the same number of repetitions of sampling and/or temperature-measuring, and sampling and/or temperature-measuring can be effected in satisfactory condition; and, PA0 (b) Easy alignment adjustment is ensured for holding the sub-lance 4 accurately in the vertical position, and in addition, prevention of the sub-lance from swinging is ensured. PA0 (1) The water supply branch pipe 54 and the water discharge branch pipe 63 are integrally connected by the fixing plate 68, and the water supply branch pipe 54 and the water discharge branch pipe 63 are respectively connected, via the fixing plate 68, to the external cooling water supply pipe 70 and the external cooling water discharge pipe 72. In order to prevent cooling water from leaking at the above-mentioned connections, it is necessary not only to conduct accurate alignment of the constitutent components 54, 63, 68, 70 and 72, but also to uniformly tighten the above-mentioned connections, thus requiring a considerable time. Furthermore, if these connections are not properly effected, strong non-uniform forces act on the bearing and oil seal mechanisms between the water supply pipe 45 and the water supply outer cylinder 48, as well as between the water discharge pipe 44 and the water discharge outer cylinder 57, thus not only impairing smooth rotation of the sub-lance 4, but also resulting in a trouble of the oil seal mechanisms, which may lead to a serious accident of cooling water leakage. PA0 (2) The weight of the external cooling water supply pipe 70 and the flexible hose connected to the external cooling water supply pipe 70, as well as the weight of the external cooling water discharge pipe 72 and the flexible hose connected to the external cooling water discharge pipe 72 are applied to the water supply branch pipe 54, the water supply outer cylinder 48, the water discharge branch pipe 63 and the water discharge outer cylinder 57, thus rendering the problem described in (1) above more serious. PA0 (3) The water supply outer cylinder 48 rotatably engages with the water supply pipe 45, and the water discharge outer cylinder 57 rotatably engages with the water discharge pipe 44. This increases the assembling time and labor of the sub-lance assembly, and requires more complicated maintenance and inspection of the sub-lance assembly. PA0 (4) Because of the many seal mechanisms such as oil seals, the reliability of sealing against cooling water decreases accordingly.
To avoid these inconveniences, prevention of the above-mentioned deflection of the sub-lance toward the main lance has been attempted through such measures as the enhancement of cooling of the sub-lance and the prevention of molten metal and molten slag from adhering onto the sub-lance. It was however impossible to ensure prevention of the aforementioned deflection of the sub-lance through these measures.
With a view to solving the above-mentioned problems involved in the conventional sub-lance, in U.S. Pat. No. 4,141,249 dated February, 1979, which corresponds to Japanese Patent Provisional Publication No. 112,204/78 dated Sept. 30, 1978 and Japanese Utility Model Provisional Publication No. 126,910/78 dated Oct. 7, 1978, there is proposed a sub-lance assembly for sampling and temperature-measuring of molten metal during refining thereof in a top-blowing oxygen converter, which comprises: a sub-lance having a concentric three-pipe structure comprising from inside to outside a gas supply pipe, a water discharge pipe and a water supply pipe; a water supply outer cylinder having a water supply branch pipe, rotatably engaging with the upper end portion of said water supply pipe; a water discharge outer cylinder having a water discharge branch pipe, rotatably engaging with the upper end portion of said water discharge pipe; said water supply branch pipe and said water discharge branch pipe being integrally connected together by a fixing plate; a drive mechanism fitted onto the outer surface of said water supply outer cylinder or said water discharge outer cylinder, for rotating said sub-lance around the axial line thereof; and a sub-lance rotation angle detector fitted to the tip of the axle of rotation of said drive mechanism, for detecting the angle of rotation of said sub-lance (hereinafter referred to as the "prior art").
According to the above-mentioned prior art, as shown in FIGS. 1 and 2, a sub-lance 4 is fitted to a sub-lance carriage 2, rotatably around the axial line of said sub-lance 4 and releasably from the sub-lance carriage 2. The sub-lance carriage 2, which is suspended by a wire rope 5, is vertically movable together with the sub-lance 4 along a guide rail 41 provided on a turning frame 1, through guide rollers, by hoisting up or down the wire rope 5 through a winch (not shown). As shown in FIG. 1, a probe 42 for sampling and temperature-measuring of a molten metal during refining thereof is releasably fitted to the lowermost end of the sub-lance 4.
As shown in FIG. 2, the sub-lance 4 has a concentric three-pipe structure comprising from inside to outside a gas supply pipe 43, a water discharge pipe 44, and a water supply pipe 45.
Also as shown in FIG. 2, a water supply outer cylinder 48 rotatably engages with the upper end portion of said water supply pipe 45 through bearings 46 and 47. The bearing 46 is fitted to the upper end portion of the water supply outer cylinder 48, and the bearing 47 is fitted to the lower end portion of the water supply outer cylinder 48. The water supply pipe 45, the water supply outer cylinder 48 and the bearings 46 and 47 are assembled so as not to come off from each other by tightening a tightening nut 49 to the outer portion of the water supply pipe 45 at the lowermost end portion of the water supply outer cylinder 48. It is therefore possible to withdraw the water supply outer cylinder 48 downward from the water supply pipe 45, by removing the tightening nut 49 from the water supply pipe 45. The gap between the water supply outer cylinder 48 and the water supply pipe 45 is water tightly sealed by oil seals 50a, 50b, 50c and 50d at positions near the upper and lower ends of the bearing 46 and the upper and lower ends of the bearing 47. The water supply pipe 45 is provided with a plurality of water supply holes 51 along the circumference thereof. The plurality of water supply holes 51 communicate with an annular groove 52 provided between the outer surface of the water supply pipe 45 and the inner surface of the water supply outer cylinder 48. The water supply outer cylinder 48 is fitted with a water supply branch pipe 54 having a flange joint 53, for connecting an external cooling water supply pipe 70 having a flange joint 69. The water supply branch pipe 54 communicates with the annular groove 52. Cooling water can therefore be supplied from the external cooling water supply pipe 70 through the water supply branch pipe 54, the water supply outer cylinder 48, the annular groove 52, and the water supply holes 51 into the water supply pipe 45.
As shown in FIG. 2, as in the water supply pipe 45 mentioned above, a water discharge outer cylinder 57 rotatably engages with the upper end portion of the water discharge pipe 44 through bearings 55 and 56. The bearing 55 is fitted to the upper end portion of the water discharge outer cylinder 57, and the bearing 56 is fitted to the lower end portion of the water discharge outer cylinder 57. The water discharge pipe 44, the water discharge outer cylinder 57 and the bearings 55 and 56 are assembled so as not to come off from each other by tightening another tightening nut 58 to the outer portion of the water discharge pipe 44 at the lowermost end portion of the water discharge outer cylinder 57. It is therefore possible to withdraw the water discharge outer cylinder 57 downward from the water discharge pipe 44 by removing the tightening nut 58 from the water discharge pipe 44. The gap between the water discharge outer cylinder 57 and the water discharge pipe 44 is water-tightly sealed by oil seals 59a, 59b, 59c and 59d at positions near the upper and lower ends of the bearing 55 and the upper and lower ends of the bearing 56. The water discharge pipe 44 is provided with a plurality of water discharge holes 60 along the circumference thereof. The water discharge holes 60 communicate with another annular groove 61 provided between the outer surface of the water discharge pipe 44 and the inner surface of the water discharge outer cylinder 57. The water discharge outer cylinder 57 is fitted with a water discharge branch pipe 63 having a flange joint 62, for connecting an external cooling water discharge pipe 72 having a flange joint 71. The water discharge branch pipe 63 communicates with the annular groove 61. Therefore, cooling water, directed from the lower end portion of the water supply pipe 45 to the lower end of the water discharge pipe 44, can be discharged through the water discharge pipe 44, water discharge holes 60, the annular groove 61, the water discharge outer cylinder 57, the water discharge branch pipe 63, and the external cooling water discharge pipe 72, to outside. The sub-lance 4 is thus cooled by cooling water.
A probe 42 for sampling and temperature-measuring of molten metal is releasably fitted, as described above, to the lowermost end of the gas supply pipe 43, and a swivel joint 64 for connecting an external gas supply pipe (not shown) rotatably engages with the uppermost end thereof. To prevent slag from coming into the probe 42 when the probe 42 passes through the slag layer covering the surface of the molten metal, pressurized gas such as air and nitrogen gas is blown into the probe 42 from the external gas supply pipe (not shown) through the swivel joint 64 and the gas supply pipe 43. The swivel joint 64 is provided with a tapped hole 65 for taking out the lead wire of the probe.
As shown in FIG. 2, the gas supply pipe 43, the water discharge pipe 44 and the water supply pipe 45 constituting the sub-lance 4 are fixed to each other. More specifically, the gas supply pipe 43 is fixed at the lower end thereof by welding to the lower end of the water discharge pipe 44, and the water discharge pipe 44 is fixed by a bolt 67 to the water supply pipe 45. The upper end portion of the water discharge pipe 44 and the upper end portion of the gas supply pipe 45 are sealed by a gland packing 66.
As shown in FIG. 2, the flange joint 53 of the water supply branch pipe 54 and the flange joint 62 of the water discharge branch pipe 63 are connected by a fixing plate 68. Connection of the flange joint 53 and the flange joint 62 is effected as follows. The water supply branch pipe 54 and the water discharge branch pipe 63 are aligned so as to achieve agreement of their axial lines, and then, the flange joint 53 of the water supply branch pipe 54 and the flange joint 62 of the water discharge branch pipe 63 are tightly connected to the flange joint 69 of the external cooling water supply pipe 70 and the flange joint 71 of the external water discharge pipe 72 by bolts and nuts (not shown) with the fixing plate 68 in between. The external cooling water supply pipe 70 and the external cooling water discharge pipe 72 are connected through respective flexible hoses (not shown) to a water source. Therefore, the sub-lance carriage 2 and the sub-lance 4 fitted on the sub-lance carriage 2 smoothly move up and down along the vertical guide rail 41 of the turning frame 1.
Since, as mentioned above, the gas supply pipe 43, the water discharge pipe 44 and the water supply pipe 45 are integrally assembled, when the sub-lance 4 is rotated in a manner as described later around the axial line thereof, the gas supply pipe 43, the water discharge pipe 44 and the water supply pipe 45 also rotate as an integral entity. The water supply outer cylinder 48, the water discharge outer cylinder 57 and the swivel joint 64 rotatably engage respectively with the upper end portions of the water supply pipe 45, the water discharge pipe 44 and the gas supply pipe 43. Furthermore, since the water supply branch pipe 54 of the water supply outer cylinder 48 and the water discharge branch pipe 63 of the water discharge outer cylinder 57 are integrally connected by the fixing plate 68, the water supply outer cylinder 48 and the water discharge outer cylinder 57 are also integrally connected. In addition, as shown in FIG. 2, a pin 73 fixed to the lower surface of the water supply outer cylinder 48 engages with a pin hole (not shown) provided in a receiving stand fixed to the sub-lance carriage 2. When the sub-lance 4 is rotated, therefore, the water supply outer cylinder 48 and the water discharge outer cylinder 57 do not rotate together with the sub-lance 4, but stand still always at prescribed positions. Thus, water supply to, and water discharge from the sub-lance 4 are carried out with no trouble.
In FIG. 2, 74 is a drive mechanism including a reduction gear, fitted via a fitting rack 74a to the water discharge outer cylinder 57, for rotating the sub-lance 4 around the axial line thereof. A chain 77 engages with a small sprocket 75 fixed to the axle of rotation of the drive mechanism 74 and with a large sprocket 76 fixed to the upper end portion of the water discharge pipe 44, so that the sub-lance 4 may be rotated by a desired angle around the axial line thereof by operating the drive mechanism 74. A sub-lance rotation angle detector 79 including a synchro device is provided at the tip of the axle of rotation of the drive mechanism 74 through another fitting rack 78. The indication of the sub-lance rotation angle detector 79 permits easy and accurate detection of an angle of rotation of the sub-lance 4 from the original position of the sub-lance 4 before rotation. It is therefore possible to accurately rotate the sub-lance 4 by the most appropriate angle of rotation for correcting a deflection of the sub-lance 4 toward the main lance, which occurs during refining of a molten metal in a top-blowing oxygen converter.
In FIGS. 1 and 2, 80 is a suspension fitting fixed to the upper end portion of the water discharge outer cylinder 57. The sub-lance 4 is engaged with or disengaged from the sub-lance carrier 2 by hoisting up or down the suspension fitting 80 with the use of a crane (not shown). More specifically, the sub-lance 4 can be easily engaged with a sub-lance carriage 2 by inserting the sub-lance 4, by hoisting down with the use of the crane, into a notch in the receiving stand fixed to the upper end portion of the sub-lance carriage 2 and into an opening in a sub-lance supporting device 40 fixed to the lower end portion of the sub-lance carriage 2. The sub-lance 4 is easily removed from the sub-lance carriage 2 by hoisting up the sub-lance 4 thus fitted to the sub-lance carriage 2 with the use of the crane, from the notch in the receiving stand and the opening in the sub-lance supporting device 40. The sub-lance supporting device 40 has the function, in cooperation with the receiving stand fixed to the upper end portion of the sub-lance carriage 2, of ensuring alignment for holding the sub-lance 4 substantially vertically, and of preventing the sub-lance 4 from swinging.
The sub-lance assembly of the prior art described above has the following excellent advantages providing remarkable effects:
However, the prior art involves the following problems:
For these reasons, the prior art, while having the above-mentioned excellent advantages, involved problems not permitting full utilization of such advantages.